more on this theme | more from this thinker
Full Idea
Modal thinking is logically equivalent to a type of counterfactual thinking. ...The necessary is that which is counterfactually implied by its own negation; the possible is that which does not counterfactually imply its own negation.
Gist of Idea
Necessity is counterfactually implied by its negation; possibility does not counterfactually imply its negation
Source
Timothy Williamson (Modal Logic within Counterfactual Logic [2010], 1)
Book Ref
'Modality', ed/tr. Hale,B/Hoffman,A [OUP 2010], p.83
A Reaction
I really like this, because it builds modality on ordinary imaginative thinking. He says you just need to grasp counterfactuals, and also negation and absurdity, and you can then understand necessity and possibility. We can all do that.
| 14531 | Rather than define counterfactuals using necessity, maybe necessity is a special case of counterfactuals [Williamson, by Hale/Hoffmann,A] |
| 14624 | Counterfactual conditionals transmit possibility: (A□→B)⊃(◊A⊃◊B) [Williamson] |
| 14625 | Necessity is counterfactually implied by its negation; possibility does not counterfactually imply its negation [Williamson] |
| 14623 | Strict conditionals imply counterfactual conditionals: □(A⊃B)⊃(A□→B) [Williamson] |
| 14626 | In S5 matters of possibility and necessity are non-contingent [Williamson] |
| 14628 | Imagination is important, in evaluating possibility and necessity, via counterfactuals [Williamson] |